Optimal Pt-Au Alloying for Efficient and Stable Oxygen Reduction Reaction Catalysts.

ABSTRACT

Stabilization of cathode catalysts in hydrogen-fueled proton-exchange membrane fuel cells (PEMFCs) is paramount to their widespread commercialization. Targeting that aim, Pt-Au alloy catalysts with various compositions (Pt95Au5, Pt90Au10, and Pt80Au20) prepared by magnetron sputtering were investigated. The promising stability improvement of the Pt-Au catalyst, manifested in suppressed platinum dissolution with increasing Au content, was documented over an extended potential range up to 1.5 VRHE. On the other hand, at elevated concentrations, Au showed a detrimental effect on oxygen reduction reaction activity. A systematic study involving complementary characterization techniques, electrochemistry, and Monte Carlo simulations based on density functional theory data enabled us to gain a comprehensive understanding of the composition-activity-stability relationship to find optimal Pt-Au alloying for maintaining the activity of platinum and improving its resistance to dissolution. According to the results, Pt-Au alloy with 10% gold represent the most promising composition retaining the activity of monometallic Pt while suppressing Pt dissolution by 50% at the upper potential limit of 1.2 VRHE and by 20% at devastating 1.5 VRHE.